Some soldiers become murderers. The military needs to figure out how to stop them

A 101st Airborne Division convoy heads out during its 2005-06 tour in Iraq.

On Nov. 5 of last year, Major Nidal Malik Hasan, an Army psychiatrist known by his superiors to have job-performance problems and by others in the government to have Islamist sympathies, opened fire at Fort Hood, Texas, killing 13 people and wounding 43 more before he was subdued. Defense Secretary Robert Gates quickly ordered a blue-ribbon panel to conduct an investigation into how such an atrocity could occur. Gates emphasized the importance of accountability. "One of the core functions of leadership is assessing the performance and fitness of people honestly and openly," he said. "Failure to do so ... may lead...